function x = fftshiftc(x)
% x= fftshiftc(x)
%
% This version of FFTSHIFT supplied in the Matlab toolbox is designed
% to shift the columns of a large matrix, much as FFTSHIFTM does
% but without the large memory requirements. The operation takes
% place on each column, one at a time. For matricies of normal
% size use FFTSHIFTM first, if memory problems develop, then try
% this. For vectors, use FFTSHIFT or FFTSHIFTM.
%
% Correction by G.F. Margrave, May 1991
%
% NOTE: This SOFTWARE may be used by any individual or corporation for any purpose
% with the exception of re-selling or re-distributing the SOFTWARE.
% By using this software, you are agreeing to the terms detailed in this software's
% Matlab source file.

% BEGIN TERMS OF USE LICENSE
%
% This SOFTWARE is maintained by the CREWES Project at the Department
% of Geology and Geophysics of the University of Calgary, Calgary,
% Alberta, Canada.  The copyright and ownership is jointly held by
% its 'AUTHOR' (identified above) and the CREWES Project.  The CREWES
% project may be contacted via email at:  crewesinfo@crewes.org
%
% The term 'SOFTWARE' refers to the Matlab source code, translations to
% any other computer language, or object code
%
% Terms of use of this SOFTWARE
%
% 1) This SOFTWARE may be used by any individual or corporation for any purpose
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[m,n] = size(x);
m1 = 1:ceil(m/2);
m2 = ceil(m/2)+1:m;
% Note: m/2+1 references the Nyquist. so the spectrum after FFTSHIFT 
% goes from -Nyquist -> DC -> one sample before + Nyquist
icol=1;
 while icol<=n
  temp=x(:,icol);
  temp(:)=[temp(m2) temp(m1)];
  x(:,icol)= temp;
  icol=icol+1;
 end  